1. Field of the Invention
This invention relates to isolation barriers and more particularly to communication across isolation barriers.
2. Description of the Related Art
Isolation barrier refers to an electrical isolation between two domains. Such isolation may be needed because during normal operation a large DC or transient voltage difference exists between the domains. For example, one domain may be “grounded” at a voltage which is switching with respect to earth ground by hundreds or thousands of volts. Another reason for such isolation is based on safety, even when the expected voltage difference between the domains is small in normal operation. An example of this would be in biomedical applications, where electrodes are taped to a patient's body; safety concerns demand an extra layer of protection between the patient and the ground of the measurement device, despite the fact that the measurement device is supposed to be properly grounded.
Isolation barriers typically consist of layers of dielectrics with good breakdown properties. Communication across isolation barriers is commonly done using optical (opto-isolators) or inductive (transformer) solutions. Capacitive isolation circuitry may also be used to transmit digital information across isolation barriers.
Various applications demand the transfer of analog information across an isolation barrier. Generally it is always possible to convert analog signals to digital on one side of the barrier, and transmit digital signals instead of analog signals directly. However, such an approach has additional component cost, additional power, and signal impairments caused by the conversion.
Thus, improvements in transmitting analog signals across isolation barriers would be desirable.